Wireline logging is a common operation in the oil industry whereby downhole electrical tools may be conveyed on a wireline (also known as an “e-line”) to evaluate formation lithologies and fluid types in a variety of boreholes. In certain wells there is a risk of the wireline cable and/or logging tools becoming stuck in the open hole due to differential sticking or cable key-seating. For example, cable key-seating may occur when the wireline cable cuts a groove into the borehole wall, and the wireline cable may become stuck in this groove. For instance, this may happen in deviated or directional wells where the wireline cable may exert considerable sideways thrust at the contact points with the borehole. Once a groove has been cut, a range of sticking mechanisms may occur, governed by geo-mechanics, geo-chemistry, drilling fluid, and lithologies. The end result may be a cancelled wireline survey or fishing operation.
In addition to cable key-seating, differential sticking may occur when there is an overbalance between hydrostatic and formation pressures in the borehole, the severity of which may be related to a number of issues. Issues may include the degree of overbalance and the presence of any depleted zones in the borehole, the character and permeability of the formations bisected by the borehole, the deviation of the borehole, since the sideways component of the tool weight adds to the sticking forces, the drilling mud properties in the borehole, since the rapid formation of thick mud cakes may trap logging tools and the wireline cable against the borehole wall, and/or the geometry of the toolstring being logged on wireline, since a long and large toolstring presents a larger cross sectional area and results in proportionally larger sticking forces. Additionally, during wireline formation sampling, the logging tools and wireline may remain stationary over permeable zones for a long period of time which also increases the likelihood of differential sticking.
To assess the cable sticking risk along a borehole, for both cable key-seating and differential sticking, physical measurements of cable contact zones and applied thrusts may be recorded. In this regard, an environmental sensing wireline standoff may be beneficial, clamped to the wireline cable to record data along the actual 3D cable path taken through the borehole. This data may improve cable sticking risk assessments and support advanced wireline tension modelling and wellbore diagnostics, to help determine borehole conditions and assess a broad range of wireline logging conveyance risks.